Conventional head-positioning mechanisms of this type have been formed, as shown in FIG. 4, in such a way that an endless tape 23 fed between a capstan 21, rotatable at a constant speed by a DC motor, and a pinch roller 22 urged thereagainst is run in a cloud loop through a pulley 24 and a tape guide 25. The endless tape 23 on its outer surface, between said pinch roller 22 and said tape guide 25, is contacted sequentially with a surface 29 of an erasing head 26, a record or play-back head 27 and a sensor 28. The endless tape 23 on its outer surface at a predetermined site has applied thereto an electrically conductive paint or is connected to an electrically conductive material for deenergizing a power source of a DC motor through short circuitry of an electronic circuit, thereby to arrest a head of the endless tape 23 at a starting position.
In this type of the head-positioning mechanism, however, the endless tape 23 is only used on its outer surface, resulting in disadvantages in that the endless tape 23 is fabricated with some difficulty. A a deenergizing means with a sensor 28 for a DC motor is complicated because of the use of the conductive endless tape 23, which leads to considerable cost and impracticality thus limiting its use in products of high grade and cost. Also, because the endless tape 23 is utilized only on its outer surface and the pulley 24 is necessarily used a longer endless tape 23 results which in turn means that a compact mechanism will not result.